Which of the following ATT has maximum CSF penetration?
**Core Concept**
The question is testing the ability to identify an antitubercular therapy (ATT) with maximum cerebrospinal fluid (CSF) penetration. CSF penetration is crucial in the treatment of tuberculous meningitis, a severe and potentially life-threatening complication of tuberculosis.
**Why the Correct Answer is Right**
Vancomycin has been used for treating meningitis due to its excellent CSF penetration. However, in the context of ATT, the correct answer is **C. Ethambutol**. Ethambutol's lipophilic nature allows it to cross the blood-brain barrier effectively, making it one of the ATTs with maximum CSF penetration. This is particularly important in treating tuberculous meningitis.
**Why Each Wrong Option is Incorrect**
* **Option A:** Isoniazid is a primary ATT but has limited CSF penetration due to its polar nature and rapid inactivation by pyridoxine.
* **Option B:** Rifampicin also has limited CSF penetration, which can lead to inadequate treatment of tuberculous meningitis.
* **Option D:** Pyrazinamide has excellent bactericidal activity in acidic environments, such as the CSF, but its penetration is not as high as Ethambutol's.
**Clinical Pearl / High-Yield Fact**
When treating tuberculous meningitis, it's essential to use ATT with good CSF penetration, such as Ethambutol, in combination with other drugs to achieve effective treatment.
**Correct Answer:** C. Ethambutol